1. Field of the Invention
The present invention relates to a light quantity control apparatus used in various camera devices such as video cameras and still cameras. Specifically, it relates to a light quantity control apparatus such as a diaphragm for regulating the amount of light in a photographing operation or a shutter for blocking the light in a photographing operation.
2. Description of the Related Arts
This type of light quantity control apparatus is comprised of a ring shape base plate integrated in the photographing lens part and having an optical axis aperture, one or a plurality of blade members revolvingly mounted to this base plate and a border on the aperture, and an electro-magnetic drive unit interlocked to the blade member and mounted to said base plate. By applying an electric current to this electro-magnetic drive unit, said blade member revolves and the aperture is blocked or the diameter of the aperture is reduced.
Tokkaihei 10-221740 describes shutter blades that block the optical axis aperture and the stop blades that regulate the size of the optical axis aperture overlapped on one base plate via an intermediate plate to adjust the quantity of light and to open and close the shutter.
Such a structure has the problem of the blade members rebounding and returning to the opposite direction when they are closed if opened or closed with force at high speed. This problem is notable with a stopper means to regulate that operation is established between the drive device and the blade members. Conventionally, the amount of rebounding is considered so the range for blade movement is enlarged. Therefore, the light quantity control apparatus becomes larger thereby creating the problem of difficulty in incorporating them into a lens barrel where space is limited.
An object of the present invention is to provide a light quantity control apparatus that has a small diameter around the optical axis of a photographic lens enabling arrangement and is capable of securely opening and closing blade members at high speeds.
In order to achieve the aforementioned purpose, this invention is composed as follows.
First, at least two drive means are mounted to the first base plate having an optical axis and shutter blades are arranged to the first base plate. Next, the light quantity apparatus comprises the overlapping intermediate plate, stop blades and the second base plate in that order, and on the first base plate, a protruding guide to guide the swinging of the shutter blades. Near the closing region and/or the opening region of this protruding guide an inclined surface is formed to gradually narrow the gap with the intermediate plate. Further, the shutter blades are formed by the vertical overlapping of at least two blade materials. The protruding guide is composed of a first guide member to guide the upper level blade and a second guide member to guide the lower level blade. The second guide member is formed with an inclined surface so it is possible to prevent the rebounding of the shutter blades when they are opened or closed.
In addition, these two guide members can be configured so that the first guide member is higher than the second guide member and that difference in height is part larger than the thickness of the shutter blade and that difference in height is smaller than the thickness of the shutter blade or the second guide member side is configured so that the oblique portion becomes larger thereby comprising an operating part in which more than two shutter blade members have little friction and a control portion which conversely has large friction for optimum closing and opening.
Also, it is possible for the structure of this invention to have a plurality of protrusion guides formed in the shutter""s opening and closing region.
First, the optimum embodiment is to have at least two drive means mounted to the first base plate having an optical axis and shutter blades arranged to the first base plate. Next, the light quantity apparatus comprises the overlapping intermediate plate, stop blades and the second base plate in that order, an interlock means to interlock one of the aforementioned drive means and the aforementioned shutter blades, a stopper means to regulate the opening region and closing region, a protruding guide to guide the swinging of the shutter blades disposed on the first base plate, and an inclined surface formed to gradually narrow the gap with the intermediate plate near the closing region and/or the opening region of this protruding guide.